This invention relates to parts that require surface roughness such as metal components used in turbine engines and more specifically to enhancing the heat transfer properties of various surfaces of the parts.
Various techniques have been devised to maintain the temperature of turbine components below critical levels. For example, coolant air from the engine compressor is often directed through the component, along one or more component surfaces. Such flow is understood in the art as a backside air flow, where coolant air is directed at a surface of an engine component that is not directly exposed to high temperature gases from combustion. In combination with backside air flow, projections from the surface of the component have been used to enhance heat transfer. These projections or bumps increase the surface area of a part and thus increase heat transfer with the use of a coolant medium that is passed along the surface. The projections are formed by one of several techniques including wire spraying and casting.
There is a need for castings and methods for forming castings with heat transfer surfaces having increased surface areas for enhanced heat transfer performance. The above mentioned need is satisfied in the present invention in which in one embodiment includes a casting having a heat transfer surface having a plurality of cavities. The cavities desirably have a density in the range of about 25 particles per square centimeter to about 1,100 particles per square centimeter and an average depth less than about 300 microns to about 2,000 microns.
Another embodiment of the present invention includes a mold for forming a pattern for use in molding a casting having a heat transfer surface. The mold includes a first mold portion and a second mold portion defining a chamber for molding the pattern. A plurality of particles are attached to a portion of the first mold portion defining the chamber. The plurality of particles have a density desirably in the range of about 25 particles per square centimeter to about 1,100 particles per square centimeter and an average particle size in the range of about 300 microns to about 2,000 microns.
Another embodiment of this invention includes a pattern for forming a casting having an enhanced heat transfer surface. This pattern corresponds to the casting and has a surface portion having a plurality of cavities similar to the casting as noted above.
Further embodiments of the present invention include a method for forming the casting described above and a method for forming the pattern described above.
Yet another embodiment of the present invention includes a method for forming a mold for use in molding the pattern for use in forming the casting described above. The method includes providing a mold having a first mold portion and a second mold portion defining a chamber for forming the pattern, and attaching a plurality of particles to a portion of the first mold portion defining the chamber. The plurality of particles comprise a density in the range of about 25 particles per square centimeter to about 1,100 particles per square centimeter and an average particle size in the range of about 300 microns to about 2,000 microns.